Fail-safe control method for engine clutch actuator and apparatus thereof

ABSTRACT

A fail-safe control method and apparatus for an engine clutch actuator includes determining whether a driving mode of a hybrid vehicle is an electric vehicle (EV) mode. An oil pressure in a cylinder of the engine clutch actuator is measured when the driving mode of the hybrid vehicle is the EV mode. The oil pressure value in the cylinder is compared with a previously stored average pressure value. A motor of the engine clutch actuator rotates to decrease the oil pressure value in the cylinder t when the oil pressure value in the cylinder is greater than the previously stored average pressure value. An engine clutch is connected to an internal combustion engine as the oil pressure value in the cylinder decreases.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of Application No. 14/108,037, filedDec. 16, 2013, which claims the benefit of priority to Korean PatentApplication No. 1 0-201 3-01 25847 filed Oct. 22, 2013, the entirecontents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a fail-safe control method for anengine clutch actuator and an apparatus thereof. More particularly, thepresent disclosure relates to a fail-safe control method for an engineclutch actuator of a hybrid vehicle by controlling an oil pressure of acylinder, and an apparatus thereof.

BACKGROUND

A hybrid vehicle is a next generation vehicle which reduces exhaust gasemissions and provides efficient gas mileage by employing motor power aswell as internal combustion engine power.

Generally, as shown in FIG. 4, in the hybrid vehicle, an engine 10, amotor 20, and an automatic transmission 30 are arranged in series. Theengine 10 and the motor 20 are connected to each other to transfer powervia an engine clutch 40.

The hybrid vehicle can drive in two different modes which may beclassified as an electric vehicle (EV) mode using only a motor power ofthe motor 20, and a hybrid electric vehicle (HEV) mode using torque ofthe engine 10 as a main power and torque of the motor 20 as an auxiliarypower.

The engine clutch actuator of a dual clutch transmission (DCT) employedin the hybrid vehicle transfers hydraulic pressure required for couplingor releasing the engine clutch by converting the torque generated fromthe motor into rectilinear movement.

When the hybrid vehicle is driven in the EV mode and while the actuatoroperates according to a characteristic of a normally closed type clutch,the clutch is released so that the motor can be used as the main powersource.

However, the engine clutch actuator installed in the hybrid vehicleaccording to the related art can only sense pressure of a cylinder and areservoir by using a pressure sensor, and supplements brake oil bydriving a piston without having any additional fail-safe strategy.

Therefore, in the hybrid vehicle according to the related art, when theengine clutch actuator fails to operate, the rectilinear movement of thepiston ceases, thus making it difficult to switch from the EV mode tothe HEV mode in the hybrid vehicle. In addition, when the engine clutchactuator does not operate during the EV mode, power consumptionincreases to maintain the EV mode since the EV mode is forced tooperate, thereby deteriorating the fuel efficiency.

SUMMARY

The present disclosure provides a fail-safe control method for an engineclutch actuator capable of returning again from an electric vehicle (EV)mode to a hybrid electric vehicle (HEV) mode even though the engineclutch actuator is broken down in the EV mode.

A fail-safe control method for an engine clutch actuator according to anexemplary embodiment of the present disclosure includes determiningwhether a driving mode of a hybrid vehicle is an electric vehicle (EV)mode. An oil pressure in a cylinder of the engine clutch actuator ismeasured when the driving mode of the hybrid vehicle is the EV mode. Anoil pressure value in the cylinder is compared with a previously storedaverage pressure value. A motor of the engine clutch actuator rotates todecrease the oil pressure value in the cylinder when the oil pressurevalue in the cylinder is greater than the previously stored averagepressure value. An engine clutch is connected to an internal combustionengine as the oil pressure value in the cylinder decreases.

The engine clutch includes a dry friction clutch.

A fail-safe control method for an engine clutch actuator according toanother embodiment of the present disclosure includes determiningwhether a driving mode of a hybrid vehicle is an electric vehicle (EV)mode. An oil pressure value in a master cylinder of the engine clutchactuator is measured when the driving mode of the hybrid vehicle is theEV mode. The oil pressure value in the master cylinder is added to apreviously stored average pressure value to obtain a new averagepressure value. The new average pressure value is substituted for thepreviously stored average pressure value.

A fail-safe control apparatus for an engine clutch actuator according toanother embodiment of the present disclosure includes a pressure sensorto measure a pressure value in a cylinder of the engine clutch actuator.A local controller determines whether a driving mode of a hybrid vehicleshould be in either an electric vehicle (EV) mode or a hybrid electricvehicle (HEV) mode by comparing the pressure value measured by thepressure sensor with an average pressure value of the cylinder in the EVmode. A motor rotates according to a command of the local controller inorder to control a pressure of the cylinder to connect an engine clutchto or release the engine clutch from an internal combustion engine.

The engine clutch includes a dry friction clutch.

The average pressure value of the cylinder in the EV mode is obtained byaveraging pressure values of the cylinder measured during a previouslystored period of time while the hybrid vehicle is driven in the EV mode.

The fail-safe control method for an engine clutch actuator according tothe present disclosure has the following advantages:

When the hybrid vehicle does not operate normally while being driven inthe EV mode, an error of the hybrid vehicle may be sensed, and thehybrid vehicle may be capable of driving in the HEV mode, thus reducingthe power consumption by maintaining the vehicle in the EV mode, therebyimproving the fuel mileage.

Further, when the engine clutch is out of order in the EV mode, themotor of the engine clutch actuator reversely rotates, so that thehybrid vehicle can be driven in the HEV mode, and thus, a fail-safecontrol may be established only with a simple structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present disclosure will now bedescribed in detail with reference to certain exemplary embodimentsthereof illustrated in the accompanying drawings which are givenhereinbelow by way of illustration only, and thus are not limitative ofthe present disclosure.

FIG. 1 is a block diagram showing a configuration of an engine clutchactuator according to an embodiment of the present disclosure.

FIG. 2 is a flowchart illustrating a method of calculating a referencevalue for determining whether an engine clutch actuator is out of orderin a fail-safe control method for an engine clutch actuator according toan embodiment of the present disclosure.

FIG. 3 is a flowchart illustrating a fail-safe control method for anengine clutch actuator according to an embodiment of the presentdisclosure.

FIG. 4 is a block diagram showing a connection relation between anengine, a motor, and a clutch of a hybrid vehicle according to therelated art.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the disclosure. Thespecific design features of the present disclosure as disclosed herein,including, for example, specific dimensions, orientations, locations,and shapes will be determined in part by the particular intendedapplication and environment.

In the figures, reference numbers refer to the same or equivalent partsof the present disclosure throughout the several figures of the drawing.

DETAILED DESCRIPTION

Hereinafter, the present disclosure will be described in detail withreference to the accompanying drawings.

FIG. 1 is a block diagram showing a configuration of an engine clutchactuator according to an embodiment of the present disclosure.

The engine clutch actuator according to an embodiment of the presentdisclosure may include a pressure sensor 100 for measuring a pressure ofa master cylinder 210, a slave cylinder 220 connected to the mastercylinder 210 through a duct 300, an local control unit (LCU) 400 forinstructing a motor of the engine clutch actuator to be rotated normallyor in reverse, and a motor 500 operated according to the instruction ofthe LCU 400. A screw 700 rotates as the motor 500 rotates, and a nut 600moves along a screw thread of the screw 700. A piston 800 applies orreleases a pressure to or from cylinder oil in the engine clutchactuator. A reservoir 1200 injects oil into the cylinder, and a troublesensor 900 measures a position of the piston 800 in the cylinder. Ahybrid control unit (HCU) 1100 determines whether the driving mode ofthe hybrid vehicle should be in either an electric vehicle (EV) mode ora hybrid electric vehicle (HEV) mode.

A process of operating the engine clutch actuator according to anembodiment of the present disclosure will be described below.

When the mode of a vehicle is switched to the EV mode, that is a pureelectric vehicle mode, while the vehicle is being driven in the HEVmode, the HCU 1100 may transfer a signal to the LCU 400 to inform theLCU 400 about the switching from the HEV mode to the EV mode. Once theLOU 400 receives the signal, the LCU 400 may separate the clutch 1000from an internal combustion engine.

The LCU 400 may provide a normal rotation command to the motor 500 ofthe engine clutch actuator. As the motor 500, which receives the normalrotation command, rotates, the screw 700 connected to a driving shaft ofthe motor 500 rotates together with the shaft. The nut 600 moves forwardalong the screw thread of the screw 700 in a direction to which thepiston is pushed. The normal rotation may be a clockwise orcounterclockwise rotation direction of the motor, but the presentdisclosure is not limited thereto. The normal rotation is a rotationaldirection in which the piston presses the cylinder oil in the engineclutch actuator as the nut 600 moves forward along the screw thread ofthe screw 700. When the motor 500 is reversely rotated, the nut 600moves back (to a left direction in FIG. 1) along the screw thread of thescrew 700 to release the pressure applied to the cylinder oil in theengine clutch actuator.

When the piston 800 moves ahead (to a right direction in FIG. 1),pressure may be applied to the cylinder oil in the cylinder 210. As thepressure is applied to the oil in the master cylinder 210, the oil inthe master cylinder 210 may flow into the slave cylinder 220 through theduct 300. The slave cylinder 220 is filled with the oil, presses arelease fork of the clutch, and separates the clutch from the engine.The motor of the vehicle is operated, thus switching the hybrid vehicleinto the EV mode.

In order to switch from the EV mode to the HEV mode, the above describedprocess may perform in reverse order. The HCU 1100 of the engine clutchactuator may instruct the LCU 400 to switch to the HEV mode, so that theLCU 400 may instruct the motor 500 to rotate in reverse in response tothe instruction. Since the motor 500 rotates in the reverse order, thenut 600 may move down along the screw thread of the screw 700. As thenut 600 moves down along the screw thread of the screw 700, the piston800 may move down together with the nut 600 so as to decrease thepressure in the master cylinder 210. As the pressure of the mastercylinder 210 is deceased, the oil of the slave cylinder 220 flows againinto the master cylinder 210 through the duct 300. The pressure appliedto the release fork is released, and the clutch 1000 is again coupled tothe engine, thus switching to the HEV mode.

According to the related art, if the engine clutch actuator does notoperate normally in the EV mode, the EV mode is compulsorily maintaineddue to the characteristics of the hybrid vehicle using the normallyclosed type clutch. As the result, the amount of power consumed by thehybrid vehicle is increased, and the fuel efficiency may bedeteriorated. In the present disclosure, the engine clutch actuator maynot operate normally in the EV by a logical defect rather than aphysical defect. Although a high-level control instructs the HCU toswitch from the EV mode to the HEV mode, the mode switching may notoperate normally.

Thus, according to the fail-safe control method for an engine clutchactuator according to an exemplary embodiment of the present disclosure,the fail-safe control method may prepare the logical defect by which theengine clutch actuator does not operate normally when switching from theEV mode to the HEV mode.

FIG. 2 is a flowchart illustrating a method of calculating a referencevalue for determining whether an engine clutch actuator is out of orderin a fail-safe control method according to an embodiment of the presentdisclosure.

When the vehicle, to which the fail-safe control method for an engineclutch actuator according to an embodiment of the present disclosure isapplied, is being driven, a controller may perform step S2-1 ofdetermining whether the vehicle is operated in the EV mode or the HEVmode. Step S2-1 may be performed by the HCU 1100 or any othercontrollers, and thus, the embodiment is not limited thereto. If thevehicle is operated in the HEV mode, the vehicle is continuouslyoperated in the HEV mode. A cylinder pressure of the engine clutchactuator, which is a reference value used for determining whether theengine clutch actuator is out of order, may not be measured. However,when the vehicle is operated in the EV mode, the vehicle may measure anoil pressure of the master cylinder 210 of the engine clutch actuatorusing the pressure sensor 100 installed inside the master cylinder 210in step S2-2. However, measuring the pressure of the master cylinder 210may not be necessary if it is possible to determine whether the cylinderpressure of the engine clutch actuator is increased based on any otherpressures. That is, the pressure sensor 100 may be installed at anylocation to determine whether the cylinder pressure of the engine clutchactuator is increased.

When the pressure sensor 100 measures the pressure in the cylinder, stepS2-3 calculates a new average pressure value by adding the measuredpressure value to the previous stored pressure in the LCU 400. Theprevious average pressure value may be a factory set initial value andstored in the LCU 400. In addition, a suitable value to determinewhether the engine clutch actuator is out of order while the vehicle isbeing driven may be the factory set initial value or may be selectedthrough repeated experiments. According to the step S2-3, the pressurevalue measured by the pressure sensor 100 and the previous average valuestored in the LOU 400 are added and divided by two to obtain the newaverage value. On the other hand, the LCU 400 may memorize the order ofmeasurements repeatedly performed by the pressure sensor 100. Then, thenew average value may be obtained by adding all values measured by thepressure sensor 100 and dividing by the number of the measurements.However, the embodiment is not limited thereto, and various methods maybe selected. Although the new average pressure value is obtained eitherby a simple calculation of the arithmetic mean of the previous averagepressure value and the measurement value; and dividing the valueobtained by adding all of the repeatedly measured values by the numberof measurements, the two calculated values gradually approach to eachother.

The LCU 400 may perform step S2-4 of storing the new average pressurevalue in the LCU 400. The new average pressure value may be stored in aninternal memory of the LCU 400 or an additionally prepared memory.However, the embodiment is not limited thereto, and if read out from thestored memory value, it does not matter where the new average pressurevalue is stored.

When the new average pressure value, which serves as a new troubledetermination reference, is stored in the LCU 400, a trouble referencemay not need to be obtained. However, while the vehicle is in the EVmode, the steps of obtaining the average pressure value may repeatduring a period of time. Since the steps are continuously repeated, theaverage pressure value may continuously vary. In addition, when thedriving mode of the vehicle switches from the EV mode to the HEV mode,the step of obtaining the average pressure value of the cylinder in theengine clutch actuator may be terminated.

FIG. 3 is a flowchart illustrating a fail-safe control method for anengine clutch actuator according to an embodiment of the presentdisclosure.

Once the vehicle starts to move, the HCU 1100 may determine whether thedriving mode of the vehicle is the HEV mode or the EV mode in step S3-1.

When the vehicle is in the HEV mode, without performing the step ofdetermining whether the engine clutch actuator is out of order, the HCU1100 may immediately terminate the process.

However, when the vehicle is in the EV mode, the engine clutch actuatoraccording to an embodiment of the present disclosure may measure the oilpressure in the cylinder of the engine clutch actuator in step S3-2. Inthis step of measuring the oil pressure in the master cylinder 210, theoil pressure may be measured by the pressure sensor 100.

After measuring the cylinder pressure, the fail-safe control method foran engine clutch actuator according to an embodiment of the presentdisclosure may obtain the average pressure value from the LCU 400 instep S3-3. In this case, the average pressure value obtained from theLCU 400 may be determined through the step of calculating the newaverage pressure value which serves as the trouble determinationreference of FIG. 2, as described above.

When the average pressure value is obtained from the LCU 400, thepressure value measured by the pressure sensor 100 is compared with theaverage value read out from the LCU 400 in step S3-4. In this step, ifthe measured oil pressure value is less than the average value obtainedfrom the LCU 400, it may be determined that the engine clutch actuatoraccording to an embodiment of the present disclosure is operatednormally. In order to measure a new pressure value when the vehicle istravelling in the EV mode, the pressure sensor 100 may perform measurethe pressure in the cylinder in step S3-2.

However, if the pressure value measured by the pressure sensor 100 isgreater than the average value obtained from the LCU 400, the LCU 400may instruct the motor 500 to rotate in a reverse direction in stepS3-5. As the motor 500 rotates in reverse, the nut 600 moves down alongthe screw thread of the screw 700 so that the piston may move backward.As a result, the pressure in the master cylinder 210 of the engineclutch actuator according to an embodiment of the present disclosure maydecrease.

As the pressure of the master cylinder 210 deceases, the driving mode ofthe vehicle switches from the EV mode to the HEV mode. Since thepressure in the master cylinder 210 of the engine clutch actuatoraccording to an embodiment of the present disclosure decreases, the oilin the slave cylinder 220 may flow into the master cylinder 210 throughthe duct 300. In addition, the decrease pressure of the slave cylinder220 may release the pressure applied to the release fork of the clutch1000. While the pressure of the release fork is released, the clutch1000 is coupled to the engine so that the vehicle is driven in the HEVmode.

When the driving mode of the vehicle is the EV mode, the fail-safecontrol method may repeat during a period of time. Further, thefail-safe control method and the process of obtaining the averagepressure value, which serves as a trouble determination reference, ofFIG. 2 may be simultaneously performed.

According to the fail-safe control method for an engine clutch actuatoraccording to an embodiment of the present disclosure, when the oilpressure of the master cylinder 210 exceeds the reference pressure, itmay be determined that the engine clutch actuator, which controls thedriving mode, is out of order, and thus, the current consumption due tothe over-travelling in the EV mode may be reduced.

As described above, the fail-safe control method for an engine clutchactuator according to an embodiment of the present disclosure has beendescribed assuming that the fail-safe control method for an engineclutch actuator is applied to a dry friction clutch, but the embodimentis not limited thereto. In addition, the embodiment may be applied toany clutch that has a similar problem.

The disclosure has been described in detail with reference to preferredembodiments thereof. However, it will be appreciated by those skilled inthe art that changes may be made in these embodiments without departingfrom the principles and spirit of the disclosure, the scope of which isdefined in the appended claims and their equivalents.

What is claimed:
 1. A fail-safe control apparatus for an engine clutch actuator comprising: a pressure sensor to measure a pressure value in a cylinder of the engine clutch actuator; a local controller to determine whether a driving mode of a hybrid vehicle should be in either an electric vehicle (EV) mode or a hybrid vehicle mode (HEV) by comparing the pressure value measured by the pressure sensor with an average pressure value of the cylinder in the EV mode; and a motor rotated according to a command of the local controller in order to control the pressure value of the cylinder to connect or release between an engine clutch and an internal combustion engine.
 2. The fail-safe control apparatus of claim 1, wherein the engine clutch includes a dry friction clutch.
 3. The fail-safe control apparatus of claim 2, wherein the average pressure value of the cylinder in the EV mode is obtained by averaging pressure values of the cylinder measured during a previously stored period of time while the hybrid vehicle is driven in the EV mode.
 4. The fail-safe control apparatus of claim 1, wherein the local controller controls the motor to rotate in reverse such that the driving mode of a hybrid vehicle switches from EV mode to HEV mode, when the pressure value measured by the pressure sensor is greater than the average pressure value of the cylinder in the EV mode.
 5. The fail-safe control apparatus of claim 4, wherein the pressure value of the cylinder is decreased by the reverse rotation of the motor to connect the engine clutch to the internal combustion engine.
 6. The fail-safe control apparatus of claim 1, wherein the cylinder of the engine clutch actuator is a master cylinder connected to a slave cylinder through a duct. 